Credit

Caption

Mural quadrant. This instrument, mounted on a wall (mural) and covering 90 degrees of angle (quadrant), is used to measure the positions of stars in the sky. The main part of the instrument is at lower left, with details of the parts across top and at right. This diagram is from 'Some Animadversions on the First Part of Hevelius' (1674) by English scientist Robert Hooke (1635-1703). This work was a criticism of a work a year earlier (Machina Coelestis, 1673) by the Polish astronomer Johannes Hevelius (1611-1687), where Hevelius described his observatory.